1. Field of the Invention
This invention relates to automatic machine tools, and more particularly to devices used in association with machine tools to hold down workpieces on the work surface to permit machining operations to be performed on the workpieces.
2. Description of the Prior Art
Computer numeric control (CNC) machining centers provide versatile machine tool movement on multiple axes for the cutting and machining a variety of materials, such as plastic, wood, poured composites such as DuPont Corian, laminated materials, aluminum and steel. A common and widely used application for CNC equipment is to automatically move router cutting and milling heads horizontally at speeds exceeding 100 inches per minute while simultaneously plunging the spinning router cutting tip, which typically is 1/4 inches in diameter, vertically downwardly into a workpiece. These machines are often called "CNC routers." The resultant cutting action when combined with motion and speed instructions from the numeric control produces cut patterns of a given configuration based upon a computer program.
The router cutting heads are moved automatically on an horizontal x axis and are plunged simultaneously vertically downwardly along a z axis into the workpiece. Since the workpiece could also move horizontally away from the router heads along the x axis and could move horizontally sideways along a y axis, the workpiece is clamped to the work surface by mechanical means or through specialized vacuum arrangement.
The cutting heads can have a straight cutting tool or complex shaped cutting tool leaving the cut edge of the workpiece with square edges, curved edges, complex edges or a combination thereof. Using this method and apparatus, the product cut from the original workpiece can be of an infinite variety of shapes, sizes and thicknesses. The product can be made in multiples or in individual cuts, producing components that, when assembled together, then result in cabinets, enclosures, boxes or other geometric shapes.
Some typical applications of the assembled work pieces are wood kitchen cabinets, furniture pieces or plastic enclosures and cabinets for electrical and electronic controls.
The CNC router allows for high speed and repeatability in tool path direction, within a tolerance of about 0.0025 inches. As improved tool cutting technology combines with faster tool movement through improved CNC technology, and computer technology provides more sophisticated programming capabilities, improvement in productivity results. In particular, computer programming facilitate rapid design changes.
A limiting factor to high production on existing CNC routers is the "set up" time required to affix the workpiece to the machine work surface. If a vacuum arrangement is used to hold down the workpiece, a gasketing system duplicating the shape of the finished cut piece is required, and this gasketing system must be created for each set up. If a mechanical clamping means is used, problems exist when the clamps interfere with tool movement over the workpiece. In either case, valuable programming and production time is lost in "setting up" to run each job.